1. Solubility.—i gram should give a clear solution with 10 c.c. of
2. Volatility.—2 grams should volatilise without leaving appreciable
residue when heated in a platinum crucible.
3. Sulphates .—The i : 20 solution, when treated with barium chloride
solution, should remain clear at least 5 minutes.
4. Metals.—The i : 20 solution should not change with ammonium
sulphide (lead, iron, etc.) and, when acidified with dilute hydrochloric acid,
should remain colourless (iron).
5. Thiocyanic Acid.—jo grams are dissolved in water and the solu-
tion made up to 500 c.c. To 5 c.c. of the solution ( = o-i gram of substance)
are added 20 c.c. of N/io-silver nitrate, the liquid being acidified with
nitric acid and a few drops of saturated ferric alum solution added.; the
excess of silver nitrate is then titrated with N/io-potassium thiocyanatc
solution until a reddish coloration appears. The difference between the
20 c.c. of silver nitrate and the number of c.c. of tlliocyanate, multiplied
by 5-9, gives percentage of HCNS, and multiplied by 5-8, percentage of CNS.
6. Ammonia.—This is determined by distillation (sc-c Fertilisers)
wit I] magnesium oxide instead of sodium hydroxide.
Chemically pure ammonium tlliocyanate contains 77-63% of HCNS and
22-37% of NH.j; the commercial pure product, which should be perfectly white
and odourless, almost always contains traces of lead, iron, and moisture. It
occurs also in a yellowish form with an. empyreurnatic odour and contaminated
with marked proportions of sulphate.
NH4V08 = 117
White or faintly yellow crystalline powder, soluble in water. The
purity and value are deduced from the determination of the vanadic acid.
Determination of the Vanadic Acid.........-T.....2 grams, dissolved in very
little water, are treated, in the hot with excess of sa.tura.ted ammonium
chloride solution, in which ammonium vanadate is insoluble; ; after 48 hours,
the liquid is filtered and the precipitate washed with, saturated ammonium
chloride solution and then with about 5°% alcohol. After being dried at
100°, the precipitate is detached as well as possible from the filter, the latter
being burned separately, its ash moistened with nitric acid and again cal-
cined ; the precipitate is then added and the whole calcined and the vanadic
anhydride weighed. I part Va()5 — 1-286 part NH4V03.
Colourless, neutral liquid of pleasant, ethereal odour, D ~- 0-875 at
15°, b.pt. 138-139°, very slightly soluble in water but readily in alcohol
or ether. It may be contaminated with amyl, ethyl, propyl and butyl
alcohols and their acetic esters and by acetic, sulphuric and hydrochloricolution must be used.